How can I do Internet Kill Switch from GUI of firewalld ? Please your kind help !

Hi. I'm new user of Linux. I'm on Linux Fedora 24 X64 cinnamon edition. I opened thread in Fedora help form about how achieve Internet kill switch. Please look to descusion within it on following link: http://www.forums.fedoraforum.org/showthread.php?t=311476 My user name in Fedora help forum is User808 also. As you see from thread, I'm not able to use command line iptables because it is deficult. I try my best but I can not. I have Idea to achieve Internet kill switch from GUI of firewalld & not sure if it is correct or not ? It seem that it is correct or correct with need for minor additions. My idea is that: After downloading VPN configuration files & set up VPN from network manager we do following: 1) open GUI of firewalld then change default zone to = drop 2) open GUI of VPN from network manager & before connect to VPN we change (from GUI of VPN within network manager) firewall zone setting of VPN to either trusted or home. 3) connect to VPN 4) after end session of VPN I have to disconnect from VPN then reopen GUI of firewalld to change back default zone to = public so as to restore normal Internet connection. Then restore zone setting of VPN from GUI of VPN in network manager to default zone. Is this valid way